Low Cost Toshiba TB6600 Driver Board

There are several variations of of the low-cost Toshiba TB6600 Motor Drive board. The one I found “most discussed” in the usual forums is the “HY-DIV268N-5A“. I am aware of 3 versions of this model: “old version”, “current version” and “newer version”. The “current version” is what I recently purchased.

Old HY-DIV268N-5A

This model is no longer available. The main discussion can be found here [link]. The main complaint is the reduction of torque while the pulse is in the low value: “The real error is in the circuitry for idle current reduction, the components winch define the delay are a 2K resistor and 1nF capacitor. Their time constant is 2 µsec, this means that the drive will go into standby mode approx. 2µsec after receiving a step pulse” [link]

If you purchase one today, this is very likely what you will get. This version attempts to fix the lost of torque by adding a 74HC123 to extend the pulse holding torque (logic chip at the left side of the board) and explained here [link].

Unfortunately, the input opto-isolator have been replaced with slower models (4N25) which limits the frequency of the the input clock. This may or may not be a problem depending on the GRBL settings used.

There is a mod to this board as explained here [link]. I plan to do this mod. (Since these are the boards I have and I purchase these before finding out the “newer” version below)

Newer HY-DIV268N-5A

This model seems an update but of lower availability. I found it in AliExpress and only by looking at the comments from customers. Externally, you may identify this model because the case has an updated brand logo [link]. Look at the customer photos.

This model fixes the slow speed of the input opto-isolator (see the 8-pin device at the lower right side of the board. It also adds 4 diodes to the output lines driver the coils of the motor to protect the board (from back EMF?). However, I have not seen reports of boards being damaged because the lacked these diodes, the datasheet does not recommend using them and some posts advise against them

MODDING THE BOARD

I have decided to mod the board by replacing the input opto-isolators with faster models and while at it, adding the following mods:

Input power capacitor with higher rated voltage capacitor. Currently it is rated at 50V which it is too closed to the rated max operating voltage of 42V-48V

Current sensing resistors. replace with higher power resistors. Some have reported failure with these resistors. Also for the OX CNC, the recommended setting in GRBL is to have the motor powered all the time, thus having high current through these resistors at all times

Other things to fix:

Thermal contact of the TB6600 to the heatsink: use fine sand paper to flatten the surface of the heatsink and reapply thermal compound

Mounting screws: add washers to the mounting holes in the TB6600 to avoid chipping the case

According to the published mod [link], the 4n25 can be replaced with the faster 6N137 on the same footprint, but with pins 1 and 8 “floating”, removing the resistor connecting to pin 6 and applying power to pin 8. I am making an adjustment to this mod by leaving the resistor connecting pin 6 and just removing the pin connection to pin 6 in the header as shown below (you can also cut pin 6 in the 6N137 for the same effect)